1. Field of the Invention
The present invention relates to a composition for the production of abrasion-resistant layers or shaped bodies with low-energy surface, to the coated substrates and shaped bodies producible therewith, and to processes for producing them and to their use.
2. Discussion of Background Information
The production of multifunctional layers with special properties, for example a combination of transparency, high abrasion resistance and specific surface chemistry properties, is today still a largely unsolved problem. For example, there are no low-energy layers which possess very high abrasion resistance apart from the known systems based on graphite or BN which are purely inorganic and are obtainable only by means of high-temperature processes. Abrasion resistance can be determined, for example, with a Taber abrasion machine.
It is known that polymers such as PTFE which have a low-energy surface are soft and have a low abrasion resistances. Although the filling of PTFE with abrasive particles improves the situation, it does not bring a satisfactory solution, since even these layers wear very rapidly in daily use. Moreover, such systems can be applied as layers only with difficulty and likewise have to be baked at relatively high temperatures.
EP 587667 (WO 92/21729) describes coatings with low-energy surface which, compared with PTFE, already have a significantly improved abrasion resistance. These coatings have a silicatic network, for which fluorinated silanes are also used. However, the low surface energy is virtually no longer detectable even after a relatively small number of cycles with a Taber abrasion machine, since the coating is a gradient layer in which the perfluorinated hydrocarbon groups which cause the low-energy surface can be found only in the uppermost region of the coating with respect to the surface.
Moreover, the coatings described in this patent, owing to the silicate network, are particularly sensitive to relatively high pH values, since materials with Si—O—Si linkages, for example glass, SiO2 or else silicic acid heteropolycondensates, are known to be degraded hydrolytically very easily by alkalis. Thus, such layers are generally unsuitable, for example, for the alkaline cleaning processes used very frequently in industry, especially for degreasing. Even when such layers are subjected to a repeated machine dishwasher operation, this leads very rapidly to a loss of the low-energy properties, because this results especially in detachment of the perfluorinated side chain-bearing silanes by hydrolysis.
It is thus an object of the invention to find abrasion-resistant low-energy layers with increased alkali resistance and hence to overcome the disadvantages explained above.
The object is achieved by a composition which comprises                a) a curable binder system comprising at least one organic polymer or oligomer with one or more functional groups or a precursor thereof,        b) at least one fluorinated polymer or oligomer having at least one functional group which is reactive with a functional group of the binder system, and        c) inorganic particles.        
The composition can be used to produce surprisingly abrasion-resistant layers with low-energy surface which additionally have improved alkali resistance. The composition is also suitable for producing shaped bodies with the same favorable properties.